Processes for producing 2,5-furandicarboxylic acid and derivatives thereof and polymers made therefrom

ABSTRACT

An integrated process is useful for producing 2,5-furandicarboxylic acid (FDCA) and/or a derivative thereof from a six-carbon sugar-containing feed. The process includes a) dehydrating a feed containing a six-carbon sugar unit, in the presence of a bromine source and of a solvent, to generate an oxidation feed that contains at least one of 5-hydroxymethylfurfural (HMF) and/or a derivative or derivatives of HMF in the solvent, together with at least one bromine containing species; b) contacting the oxidation feed from step (a) with a metal catalyst and with an oxygen source under oxidation conditions to produce an oxidation product mixture of at least FDCA and/or a derivative thereof, the solvent, and a residual catalyst: c) purifying and separating the mixture obtained in step (b) to obtain FDCA and/or a derivative thereof and the solvent; and d) recycling at least a portion of the solvent obtained in step (c) to step (a).

TECHNICAL FIELD

The present invention relates to oxidation methods for producing2,5-furandicarboxylic acid from six carbon sugars as may be obtainedfrom biological sources, and especially to methods which employ ahomogeneous catalyst in a solvent.

BACKGROUND ART

The use of natural products as starting materials for the manufacture ofvarious large-scale chemical and fuel products which are presently madefrom petroleum- or fossil fuel-based starting materials, or for themanufacture of biobased equivalents or analogs thereto, has been an areaof increasing importance. For example, a great deal of research has beenconducted into the conversion of natural products into fuels, as acleaner and, certainly, as a more sustainable alternative to fossil-fuelbased energy sources.

Agricultural raw materials such as starch, cellulose, sucrose or inulinare inexpensive and renewable starting materials for the manufacture ofhexoses, such as glucose and fructose. It has long been appreciated inturn that glucose and other hexoses, in particular fructose, may beconverted into other useful materials, such as5-hydroxymethyl-2-furaldehyde, also known as 5-hydroxymethylfurfural orsimply hydroxymethylfurfural (HMF):

The sheer abundance of biomass carbohydrates available provides a strongrenewable resource base for the development of commodity chemical andfuel products based on HMF. For example, U.S. Pat. No. 7,385,081, issuedin June 2008 to Gong, estimates, for example, that of the approximately200 billion tons of biomass produced annually, 95% was in the form ofcarbohydrates, and only 3 to 4% of the total carbohydrates were thenused for food and other purposes.

In view of this fact, and due to HMF's various functionalities, it hasbeen proposed that the HMF thus obtainable from hexoses such as fructoseand glucose, could be utilized to produce a wide range of productsderived from renewable resources, such as polymers, solvents,surfactants, pharmaceuticals, and plant protection agents. HMF has inthis regard been proposed, as either a starting material orintermediate, in the synthesis of a wide variety of compounds, such asfurfuryl dialcohols, dialdehydes, esters, ethers, halides and carboxylicacids.

A number of the products discussed in the literature derive from theoxidation of HMF or of certain derivatives of HMF, especially, ether andester derivatives of HMF. One such product, 2,5-furandicarboxylic acid(FDCA, also known as dehydromucic acid), has been discussed as abiobased, renewable analog to terephthalic acid in the production ofsuch multi-megaton polyester polymers as poly(ethylene terephthalate) orpoly(butylene terephthalate), as well as a useful monomer for makingother commercially valuable polymeric products, for example, inpolyamides. FDC A esters have also recently been evaluated asreplacements for phthalate plasticizers for PVC, see, e.g., WO2011/023491A1 and WO 2011/023590A1, both assigned to Evonik Oxeno GmbH,as well as R. D. Sanderson et al., Journal of Appl. Pol. Sci. 1994, vol.53, pp. 1785-1793.

While FDCA and its derivatives (for example, the ester derivatives justmentioned) have attracted a great deal of recent commercial interest,with FDCA being identified, for instance, by the United StatesDepartment of Energy in a 2004 study as one of 12 priority chemicals forestablishing the “green” chemical industry of the future, the potentialof FDCA (due to its structural similarity to terephthalic acid) to beused in making polyesters, for example, has been recognized at least asearly as 1946, see GB 621,971 to Drewitt et al, “Improvements inPolymer”.

Unfortunately, viable commercial-scale processes have proven elusive. Athreshold challenge has been the development of a commercially viableprocess to make an HMF or HMF ester or ether derivative from which FDCAcould be prepared. Acid-based dehydration methods have long been knownfor making HMF, being used at least as of 1895 to prepare HMF fromlevulose (Dull, Chem. Ztg., 19, 216) and from sucrose (Kiermayer, (Chem.Zig., 19, 1003). However, these initial syntheses were not practicalmethods for producing HMF due to low conversion of the starting materialto product. Inexpensive inorganic acids such as H₂SO₄, H₃PO₄, and HClhave been used, but these are used in solution and are difficult torecycle. In order to avoid the regeneration and disposal problems, solidsulfonic acid catalysts have also been used. The solid acid resins havenot proven entirely successful as alternatives, however, because of theformation of deactivating humin polymers on the surface of the resins.Still other acid-catalyzed methods for forming HMF from hexosecarbohydrates are described in Zhao et al., Science, Jun. 15, 2007, No.316, pp. 1597-1600 and in Bicker et al., Green Chemistry, 2003, no. 5,pp. 280-284. In Zhao et al., hexoses are treated with a metal salt suchas chromium (IT) chloride in the presence of an ionic liquid, at 100degrees Celsius for three hours to result in a 70% yield of HMF, whereasin Bicker et al., sugars are dehydrocyclized to HMF at nearly 70%reported selectivity by the action of sub- or super-critical acetone anda sulfuric acid catalyst

In the acid-based dehydration methods, additional complications arisefrom the rehydration of HMF, which yields by-products such as levulinicand formic acids. Another unwanted side reaction includes thepolymerization of HMF and/or fructose resulting in humins, which aresolid waste products and act as catalyst poisons where solid acid resincatalysts are employed, as just mentioned. Further complications mayarise as a result of solvent selection. Water is easy to dispose of anddissolves fructose, but unfortunately, low selectivity and the formationof polymers and humins increases under aqueous conditions.

In consideration of these difficulties and in further consideration ofprevious efforts toward a commercially viable process for making HMF,Sanborn et al. in US Published Patent Application 2009/0156841A1(Sanborn et al) describe a method for producing “substantially pure” HMFby heating a carbohydrate starting material (preferably fructose) in asolvent in a column, continuously flowing the heated carbohydrate andsolvent through a solid phase catalyst (preferably an acidic ionexchange resin) and using differences in the elution rates of HMF andthe other constituents of the product mixture to recover a“substantially pure” HMF product, where “substantially pure” isdescribed as meaning a purity of about 70% or greater, optionally about80% or greater, or about 90% or greater. An alternative method forproducing HMF esters performs the conversion in the presence of anorganic acid, which can also serve as the solvent Acetic acid ismentioned in particular as a solvent for fructose. The resultingacetylated HMF product is reported to be “more stable” than HMF, becauseupon heating HMF is described as decomposing and producing byproducts“that are not easily isolated or removed,” page 4, paragraph 0048.

Further, the acetylated HMF is said to be more easily recovered bydistillation or by extraction, though filtration, evaporation andcombinations of methods for isolating the HMF esters are also described(page 2, para. 0017). The product, HMF ester which may include someresidual HMF, can then be mixed in one embodiment with organic acid,cobalt acetate, manganese acetate and sodium bromide and oxidized toFDCA in the presence of oxygen and at elevated temperatures andpressures. In the examples, a Parr reactor is used for performing theoxidation.

Still other derivatives of HMF have been prepared for subsequentoxidation to FDCA or to the ester derivatives of FDCA, as shown, forexample, in U.S. Pat. No. 8,558,018 to Sanborn et al., wherein5-(alkoxymethyl)furfural (AMF), 5-(aryloxymethyl)furfural,5-(cycloalkoxymethyl)furfural and 5-(alkoxycarbonyl)furfural compoundsare described as oxidized in the presence of dissolved oxygen and aCo(II), Mn(II), Ce(III) salt catalyst or mixtures thereof to provideFDCA and various other related materials. The products that can be madewill understandably vary dependent on the starting material or mix ofstarting materials, but can include 2,5-furandicarboxylic acid (FDCA)with the inclusion of bromide. When the reactant is an ether derivativeof HMF, the products are surprisingly ester derivatives where eitherboth the ether and aldehyde functional groups have been oxidized, orjust the ether function group may be oxidized producing one or both of5-ester-furan-2-acids (i.e., 5-alkoxycarbonylfurancarboxylic acids) or5-ester-furan aldehydes, (i.e., alkoxycarbonylfurfurals a. k. a5-(alkoxycarbonyl)furfural).

In relation to the second part of a process for making FDCA fromcarbohydrates via HMF or a suitable HMF derivative, for example, anether or ester derivative as just described, a number of otherreferences have also proposed an oxidation in the presence of verysimilar catalyst systems to that proposed in Sanborn et al. Thus, forexample, in U.S. Pat. No. 7,956,203 to Grushin et al. (E.I. DuPont deNemours and Company), furan-2,5-dicarboxylic acid (FDCA) is described asmade by contacting an alcohol/aldehyde such as HMF with an oxidant inthe presence of a metal bromide catalyst to form a dialdehyde,optionally isolating the dialdehdyde, then contacting the dialdehydewith an oxidant in the presence of a metal bromide catalyst to form anacid/aldehyde, with optionally isolating the acid/aldehyde, and finallycontacting the acid/aldehyde with an oxidant in the presence of a metalbromide catalyst to form the diacid. Grushin contemplates carrying outthis process in the presence of a solvent or solvent mixture comprisingan aliphatic C₂-C₆ monocarboxylic acid, which is preferably acetic acid.

The metal bromide catalyst used in Grushin's process comprises a solubletransition metal compound and soluble bromine-containing compound. Onemetal or a combination of two or more metals may be used, with thetransition metal component preferably being cobalt and/or manganese,optionally but preferably further comprising zirconium. Each of themetal components (Co, Mn, Zr) can be provided in any of their knownionic or combined forms, with metal acetate tetrahydrates beingmentioned as preferred. The source of bromide “can be any compound thatproduces bromide ions in the reaction mixture”, col. 6, lines 32-33,e.g., hydrogen bromide, hydrobromic acid, sodium bromide, elementalbromine, benzyl bromide, and tetrabromoethane, with sodium andhydrobromic acid being mentioned as preferred.

In U.S. Pat. No. 8,242,292 to Yutaka et al. (Canon Kabushiki Kaisha), asimilar method is described for producing FDCA, wherein yieldimprovements are attributed to the regulation of water content in theoxidation process. HMF is again brought into contact with an oxidant inan organic acid solvent in the presence of bromine and a metal catalystwhile removing water produced by the reaction. The metal catalystpreferably contains Co or Mn, but more preferably contains both of Coand Mn, while Br is described as serving as an initiator for thereaction and as advancing the reaction while reducing Co as a mainoxidation catalyst through ion discharge. The manner in which bromine isintroduced is not addressed by Tutaka et al., but each of the examplesemploys sodium bromide.

U.S. Pat. No. 8,519,167 to Mufoz de Diego et al. (Furanix Technologies BV) describes a method for the preparation of FDCA and/or an alkyl esterof FDCA through contacting a feed comprising a starting materialselected from 5-alkoxymethylfurfural, 2,5-di(alkoxymethyl)furan and amixture thereof, and optionally further containing HMF, with an oxidantin the presence of an oxidation catalyst comprising at least one ofcobalt and manganese (and preferably containing both) as well as asource of bromine, preferably a bromide. The bromine source is describedessentially as in Grushin, as including any compound that producesbromide ions in the reaction mixture, with hydrobromic acid and/orsodium bromide being preferred. The starting materials are described asprepared from carbohydrates, then through isolation of a feed forcontact with the oxidant.

U.S. Pat. No. 8,791,278 to Shaikh et al. (Eastman Chemical Company)describes a process for making FDCA and/or a dry purified FDCA throughoxidizing at least one oxidizable compound in an oxidizable raw materialstream in the presence of an oxidizing gas stream, solvent stream and atleast one catalyst system. The catalyst system is described aspreferably comprised of at least one selected from, but not beinglimited to, cobalt, bromine and manganese compounds which are soluble inthe selected oxidation solvent. The bromine component may be added aselemental bromine, in combined form, or as an anion. “Suitable” sourcesof bromine include hydrobromic acid, sodium bromide, ammonium bromide,potassium bromide, and tetrabromoethane, with hydrobromic acid andsodium bromide again listed as preferred (as in each of Grushin, Yutakaand Shaikh).

Those familiar with the manufacture of terephthalic acid will be veryfamiliar with the use of such solvent-soluble Co/Mn/Br catalyst systemsas taught in the several references just summarized. Metal bromidecatalysts employing Co and Mn, and in some cases additional metals suchas Zr and/or Ce, have been widely commercially used for the liquid-phaseoxidation of para-xylene to terephthalic acid. While there has been somelimited work done on alternative catalyst systems for converting HMF(and/or an HMF derivative, e.g, an HMF ether or ester derivative) toFDCA, yet because the HMF to FDCA conversion has been evaluated with theoverall objective in mind of making a renewable analog to terephthalicacid, it is perhaps not surprising that the catalysts proposed for usein most of the HMF/HMF derivative to FDCA art, as well as the generalreaction parameters and process steps described therein, mirror or atleast are strongly correlated to the p-xylene oxidation art. There wouldbe distinct and obvious advantages to a manufacturer's developing andimplementing an HMF/HMF derivative to FDCA oxidation technology thatclosely resembles the existing p-xylene to terephthalic acid oxidationtechnology that has been so widely used, including, but not beinglimited to, easing the transition for operations personnel accustomed tothe p-xylene process, making use of longstanding catalyst supplyrelationships and facilitating the use of excess terephthalicacid-manufacturing capacity and associated depreciated capital assets.

However, there is a need for a new, more efficient and more costeffective process that converts sugars to furandicarboxylic acid (FDCA)and/or valuable derivatives thereof, for example, diether, diester,ether-acid, ether-ester, ester-acid, ester-aldehyde, ether-aldehyde,ether-acetal, ester-acetal, acetal-acid, alcohol-acid, alcohol-ester,alcohol-acetal, diol, diacetal and aldehyde-acetal derivatives, that canbe used as monomers in polymeric syntheses or as intermediates in othersyntheses.

SUMMARY OF THE INVENTION

In one aspect of the present invention, there is an integrated processfor producing 2,5-furandicarboxylic acid and/or a derivative thereoffrom a six carbon sugar-containing feed, comprising:

a) dehydrating a feed comprising a six-carbon sugar unit, in thepresence of a bromine source and of a solvent, at an elevatedtemperature and for a time sufficient to generate an oxidation feedcomprised of at least one of 5-hydroxymethylfurfural, an etherderivative of 5-hydroxymethylfurfural or an ester derivative of5-hydroxymethylfurfural in the solvent, together with at least onebromine containing species;

b) contacting the oxidation feed from step (a) with a metal catalyst andwith an oxygen source at an elevated temperature for a time sufficientto produce an oxidation product mixture comprising 2,5-furandicarboxylicacid (FDCA) and/or a derivative of 2,5-furandicarboxylic acid, thesolvent, and a residual catalyst;

c) purifying and separating the mixture obtained in step (b) to obtainFDCA and/or a derivative of 2,5-furandicarboxylic acid and the solvent;and

d) recycling at least a portion of the solvent obtained in step (c) tostep (a).

In certain embodiments, an integrated process of the present inventionmore generally includes regulating the amount of bromine in theoxidation step by adding to or removing bromine from the oxidation feedprior to the oxidation step.

In certain embodiments, the oxidation feed comprises one or more ofinorganic bromide and organic bromide.

In certain embodiments, the metal catalyst for the oxidation stepcomprises one or more transition metals.

In certain embodiments, the metal catalyst comprises either or both ofCo and Mn.

In certain embodiments, the metal catalyst comprises Zr in addition toeither or both of Co and Mn.

In certain embodiments, the metal catalyst comprises Ce in addition toeither or both of Co and Mn.

In certain embodiments, HBr is employed as a source of bromine in thedehydration step.

In certain embodiments, HBr (as hydrobromic acid) is used as an acidcatalyst for the dehydration step, and concurrently serves as a brominesource in the dehydration step and for a subsequent Mid-Century-typeoxidation.

In certain embodiments, the bromine source in the dehydration stepincludes at least one bromine-containing material obtained from theoxidation step and recycled back to the dehydration step.

In certain embodiments, the feed to the process comprises one or more ofstarch, amylose, galactose, cellulose, hemicellulose, inulin, fructan,glucose, fructose, sucrose, maltose, cellobiose, lactose, and sugaroligomers.

In certain embodiments, the feed is fructose syrup, crystallinefructose, high fructose corn syrup, crude fructose, purified fructose ormolasses.

In certain embodiments, as for example based on the dehydration of asix-carbon sugar-containing feed in the form of a product, byproduct orprocess intermediate stream as received from an existing, operating wetor dry grain milling process, the process further comprisesconcentrating or diluting the oxidation feed by the removal or additionof solvent prior to the oxidation step.

In certain embodiments, the solvent comprises acetic acid or a mixtureof acetic acid and water.

In certain embodiments, the process further includes regulating thewater content of the feed to the dehydration step and of the oxidationfeed generated therefrom.

In certain embodiments, the water content of a six-carbonsugar-containing feed in the form of a product, byproduct or processintermediate stream as received from an existing, operating wet or drygrain milling process is increased by addition of water thereto toimprove the yield of furanic species from the six-carbon sugars thatwill ultimately be oxidized to FDCA and/or a derivative thereof in thesubsequent oxidation step, and the water content of the oxidation feedis adjusted to a lower concentration than supplied to the dehydrationstep.

In certain embodiments, the solvent further comprises abromine-containing ionic liquid, for example, a 1-alkylpyridiniumbromide or 1,3-dialkylimidazolium bromide.

In certain embodiments, the feed is dehydrated in the presence of aC₁-C₅ alcohol.

In other embodiments of an integrated process according to the presentinvention, a portion of the product from the dehydration step is used toproduce certain derivative co-products from HMF, with optionallyoxidizing at least a portion of these derivative co-products from HMF toalso produce FDCA or derivatives thereof.

In one such embodiment, an integrated process is provided includingdehydrating a feed comprising a six-carbon sugar unit in the presence ofa solvent, at an elevated temperature and for a time sufficient toprovide a dehydration product including at least one of5-hydroxymethylfurfural, an ether derivative of 5-hydroxymethylfurfuralor an ester derivative of 5-hydroxymethylfurfural in the solvent;hydrogenating at least a portion of the dehydration product as a wholeor of one or more of the 5-hydroxymethylfilrfural, ester or etherderivative of 5-hydroxymethylfurfural materials in the dehydrationproduct to form a reduced derivative or derivatives therefrom; oxidizinga portion of the dehydration product not hydrogenated, if any, andincluding oxidizing at least a portion of the reduced derivatives, bycombination with an oxygen source in the presence of a metal catalyst atan elevated temperature and for a time sufficient to produce anoxidation product comprising 2,5-furandicarboxylic acid and/or aderivative thereof, the solvent and a residual catalyst; purifying andseparating the mixture obtained from the oxidation step to obtain FDCAand/or a derivative thereof and the solvent; and recycling at least aportion of the solvent to the dehydration step, wherein either or bothof the dehydration and hydrogenation steps are carried out in thepresence of a bromine source so that a bromine-containing species, areduced bromine-containing species or both are included in the materialsfed to the oxidation step.

In another such co-product embodiment, an integrated process is providedwhich includes dehydrating a feed comprising a six-carbon sugar unit inthe presence of a solvent, at an elevated temperature and for a timesufficient to provide a dehydration product including at least one of5-hydroxymethylfurfural, an ether derivative of 5-hydroxymethylfurfuralor an ester derivative of 5-hydroxymethylfurfural in the solvent;hydrogenating at least a portion of the dehydration product as a wholeor of one or more of the 5-hydroxymethylfurfural, ester or etherderivative of 5-hydroxymethylfurfural materials in the dehydrationproduct to form a reduced derivative or derivatives therefrom;etherifying at least a portion of the reduced derivative or derivativesby combination with an alcohol under conditions effective for forming anether derivative from a reduced derivative of 5-hydroxymethylfurfural;oxidizing a portion of the dehydration product not hydrogenated, if any,and optionally including oxidizing at least a portion of the reducedderivatives from the hydrogenation step, at least some of the etherderivatives from the etherification step or both reduced derivativesfrom the hydrogenation step and ether derivatives from theetherification step, by combination with an oxygen source in thepresence of a metal catalyst at an elevated temperature and for a timesufficient to produce an oxidation product comprising FDCA and/or aderivative thereof, the solvent and a residual catalyst; purifying andseparating the oxidation product mixture to obtain FDCA and/or aderivative thereof and the solvent; and recycling at least a portion ofthe solvent to the dehydration step, wherein any one or more of thedehydration, hydrogenation and etherification steps are carried out inthe presence of a bromine source so that at least one of abromine-containing species, a reduced bromine-containing species and anetherified reduced bromine-containing species is or are included in thematerials fed to the oxidation step.

In another aspect, the present invention relates to the preparation ofmonomeric derivatives of the FDCA produced by an integrated process assummarized above, wherein FDCA is esterified with a C₁-C₁₂ aliphaticalcohol or a C₁-C₁₂ aliphatic diol, under conditions effective forcarrying out the esterification and optionally in the presence of asuitable esterification catalyst.

In another aspect, the present invention relates to the preparation of apolyester by transesterification of ester derivatives of2,5-furandicarboxylic acid with a C₂-C₁₂ aliphatic diol or a polyol andoptionally at least one of a polyalkylene ether glycol, a polyfunctionalacid or a polyfunctional hydroxyl acid.

In yet another aspect, the present invention relates to preparing asemi-crystalline prepolymer of isoidide with a 2,5-furandicarboxylicacid ester and optionally 1,4-butanediol or 2,3-butanediol by meltpolymerization, then performing solid state post condensation on thesemi-crystalline prepolymer.

In an aspect, the integrated process further comprises preparing a furanbased polyamide compositions comprising contacting an aliphatic oraromatic diamine with 2,5-furandicarboxylic acid and/or derivativesthereof, optionally in the presence of a solvent.

In yet another aspect, the present invention relates to the preparationof a furan based polyamide composition, comprising the steps ofdissolving an aromatic diamine monomer in a polar solvent to form adiamine solution under inert atmosphere, wherein the solvent is selectedfrom the group consisting of dimethyl acetamide, dimethyl formamide anddimethyl sulfoxide; adding an aromatic diacid monomer or aromatic diacidderivative component in the form of 2,5-furandicarboxylic acid from theintegrated process of the present invention or in the form of aderivative of FDCA from the integrated process to the diamine solutionat a temperature in the range of −5 to 35 degrees Celsius to form areaction mixture; continuing the reaction until there is no furtherincrease in temperature or until a desired viscosity of the reactionmixture is achieved; and isolating the polymer from the reactionmixture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one illustrative embodiment of anintegrated process for making 2,5-furandicarboxylic acid and/or aderivative thereof.

FIG. 2 is a schematic diagram of a second illustrative embodiment of anintegrated process for making 2,5-fiirandicarboxylic and/or a derivativethereof.

FIG. 3 is a schematic diagram of a third illustrative embodiment of anintegrated process for making 2,5-furandicarboxylic acid and/or aderivative thereof, together with one or more reduced derivatives of HMFand/or HMF derivatives as co-products.

FIG. 4 schematically depicts a fourth illustrative embodiment of anintegrated process for making 2,5-furandicarboxylic acid and/or aderivative thereof, together with one or more reduced derivatives and/orone or more etherified reduced derivatives of HMF and/or HMF derivativesas co-products.

FIG. 5 schematically depicts a process for making further products fromthe FDCA and/or a derivative of FDCA from an integrated process as shownin FIG. 1, though it will of course be understood that the furtherproducts may be equally made from the FDCA produced according to any ofthe other embodiments schematically shown in FIGS. 2-4.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The disclosures of all patent and non-patent literature referencedherein are hereby incorporated in their entireties.

The term “furandicarboxylic acid” is used interchangeably with furandicarboxylic acid; 2,5-furandicarboxylic acid; 2,4-furan dicarboxylicacid; 3,4-furandicarboxylic acid; and 2,3-furandicarboxylic acid.2,5-furandicarboxylic acid (FDCA), also known as dehydromucic acid, isan oxidized furan derivative

2,5-Furandicarboxylic acid IUPAC name Furan-2,5-dicarboxylic acid Othernames Dehydromucic acid Identifiers CAS number 3238-40-2 PubChem 76720

A “derivative of 2,5-furandicarboxylic acid” as used above and elsewhereherein shall be understood to include, but not limited to ether, acetaland ester derivatives of 2,5-furandicarboxylic acid and associated2,5-furandicarboxylic acid precursors, such as 5-hydroxymethylfurfural,2,5-diformylfuran, and 5-formyl-2-furancarboxylic acid. For example, a“derivative of 2,5-furandicarboxylic acid” may include any derivativecombinations thereof, for example, diether, diester, ether-acid,ether-ester, ester-acid, ester-aldehyde, ether-aldehyde, ether-acetal,ester-acetal, acetal-acid, alcohol-acid, alcohol-ester, alcohol-acetal,diol, diacetal and aldehyde-acetal derivatives.

A “six-carbon sugar unit” as used above and elsewhere herein shall beunderstood as comprising at least one of a six-carbon sugar, an oligomerof a six-carbon sugar, and/or a polymer of a six-carbon sugar.

A “bromine source” as used above and elsewhere herein shall beunderstood to be any compound that produces bromide ions or radicals inthe reaction mixture, e.g., hydrogen bromide, hydrobromic acid, sodiumbromide, elemental bromine, benzyl bromide, 5-(bromomethyl)furfural andtetrabromoethane.

A “bromine-containing species” as used above and elsewhere herein shallbe understood as comprising one or more of inorganic bromides such asHBr; metal bromides including but not being limited to lithium bromide,sodium bromide, potassium bromide, magnesium bromide, calcium bromide,cobalt bromide and manganese bromide; and organic bromides such as, butnot being limited to, 5-(bromomethyl) furfural and derivatives thereof,and brominated furanic oligomers.

A “residual catalyst” as used above and elsewhere herein shall beunderstood as comprising one or more of bromine-containing species andmetal catalyst.

As used in this application, the singular forms “a”, “an” and “the”include plural references unless the context clearly indicatesotherwise. The term “comprising” and its derivatives, as used herein,are similarly intended to be open ended terms that specify the presenceof the stated features, elements, components, groups, integers, and/orsteps, but do not exclude the presence of other unstated features,elements, components, groups, integers and/or steps. This understandingalso applies to words having similar meanings, such as the terms“including”, “having” and their derivatives. The term “consisting” andits derivatives, as used herein, are intended to be closed terms thatspecify the presence of the stated features, elements, components,groups, integers, and/or steps, but exclude the presence of otherunstated features, elements, components, groups, integers, and/or steps.The term “consisting essentially of”, as used herein, is intended tospecify the presence of the stated features, elements, components,groups, integers, and/or steps, as well as those that do not materiallyaffect the basic and novel characteristic(s) of stated features,elements, components, groups, integers, and/or steps Terms of degreesuch as “substantially”, “about” and “approximately” as used herein meana reasonable amount of deviation of the modified term (beyond thatdegree of deviation understood by the precision (significant figures)with which a quantity is expressed) such that the end result is notsignificantly changed. These terms of degree should be construed asincluding a deviation of at least plus or minus five (5) percent fromthe stated value, provided this deviation would not negate the meaningof the term modified.

The term “biologically-derived” as used herein is used interchangeablywith “biobased” or “bioderived”, and “biologically-derived”. “biobased”and “bioderived” shall all be understood as referring to any chemicalcompounds, including monomers and polymers, that are obtained, in wholeor in any part, from any renewable resources including but not limitedto plant, animal, marine materials or forestry materials. The “biobasedcontent” of any such compound shall be understood as the percentage of acompound's carbon content determined to have been obtained or derivedfrom such renewable resources by ASTM Method D6866. In this regard ASTMMethod D6866, similar to radiocarbon dating, compares how much of adecaying carbon isotope remains in a sample to how much would be in thesame sample if it were made of entirely recently grown materials.Samples are combusted in a quartz sample tube and the gaseous combustionproducts are transferred to a borosilicate break seal tube. In onemethod, liquid scintillation is used to count the relative amounts ofcarbon isotopes in the carbon dioxide in the gaseous combustionproducts. In a second method, 13C/12C and 14C/12C isotope ratios arecounted (14C) and measured (13C/12C) using accelerator massspectrometry. Zero percent 14C indicates the entire lack of 14C atoms ina material, thus indicating a fossil (for example, petroleum based)carbon source. One hundred percent 14C, after correction for thepost-1950 bomb injection of 14C into the atmosphere, indicates a moderncarbon source. ASTM D6866 effectively distinguishes between biobasedmaterials and petroleum derived materials in part because isotopicfractionation due to physiological processes, such as, for example,carbon dioxide transport within plants during photosynthesis, leads tospecific isotopic ratios in natural or biobased compounds. By contrast,the 13C/12C carbon isotopic ratio of petroleum and petroleum derivedproducts is different from the isotopic ratios in natural or bioderivedcompounds due to different chemical processes and isotopic fractionationduring the generation of petroleum. In addition, radioactive decay ofthe unstable 14C carbon radioisotope leads to different isotope ratiosfirst in biobased products compared to petroleum products.

The term “FDCA-forming furanics” as used herein refers to furan ringcontaining monomeric and dimeric molecules with molecular structuredirectly presumed to form FDCA throughout the course of oxidation.Examples of FDCA-forming furanics, with acetic acid as solvent, include,but are not limited to, 5-(hydroxymethyl)furfural,5-(acetoxymethyl)furfural, and 5,5′(oxy-bi s(methylene))bis-2-furfural.Examples of non-FDCA forming furanics include, but are not limited to,furfural, 2-(hydroxyacetyl)furan, and 2-(acetoxyacetyl)furan.

The present invention may be more completely understood by describingcertain embodiments in greater detail. These embodiments are not to betaken as limiting the scope and breadth of the current invention as moreparticularly defined in the claims that follow, but are illustrative ofthe principles behind the invention and demonstrate various ways andoptions for how those principles can be applied in carrying out theinvention.

Thus, unless otherwise indicated, any definitions or embodimentsdescribed in this or in other sections are intended to be applicable toall embodiments and aspects of the subjects herein described for whichthey would be suitable according to the understanding of a person ofordinary skill in the art.

Turning now to FIG. 1, an integrated process 10 of the present inventionis schematically depicted in a first illustrative embodiment. A feed 12comprising a six-carbon sugar unit is dehydrated in a dehydration step14 in the presence of a bromine source and of a solvent at an elevatedtemperature and for a time sufficient to generate an oxidation feed 16comprised of at least one of 5-hydroxymethylfurfural (HMF), an etherderivative of HMF (which is capable of being oxidized to form FDCA or aderivative of FDCA in a Mid-Century type process) or an ester derivativeof HMF (which has also been demonstrated as capable of oxidation to formFDCA or a derivative of FDCA in a Mid-Century type process) in thesolvent, together with at least one bromine-containing species.

The feed 12 can be any source of a six-carbon sugar unit. In anembodiment, the feed 12 can comprise one or more of starch, amylose,galactose, cellulose, hemicellulose, inulin, fructan, glucose, fructose,sucrose, maltose, cellobiose, lactose, and sugar oligomers. Where theintegrated process 10 is implemented in the context of an existing plantwherein such sources of hexose carbohydrates already exist, the feed 12may be obtained from one or a combination of already existing hexosesources, for example, in the form of a product, byproduct or processintermediate stream as received from an existing, operating wet or drygrain milling process, fructose syrup, crystalline fructose, highfructose corn syrup, crude fructose, purified fructose or molasses.

In certain embodiments, the amount of water in the feed 12 may beadjusted from the water content of a product, byproduct or processintermediate stream as received from an existing, operating wet or drygrain milling process, for example, by combining a plurality of suchstreams in certain proportions and/or by means of recycling water fromthe oxidation step 18 via stream 26, to regulate the amount of waterentering the process 10 in feed 12.

We have found in this regard that the yield of FDCA-forming furanicsfrom the six-carbon sugars in a feed 12 is increased in the dehydrationstep 14 by increasing the water content of the feed 12 to a certainpoint, beyond which, however, the yield of FDCA-forming furanics beginsto decline. In the dehydration of an aqueous fructose solution at 150degrees Celsius with 2 mol percent of HBr added, for example, a watercontent of from about 8 to about 10 weight percent in a mixture of waterand acetic acid (the latter being provided at least in part by recyclein the context of the present invention) appeared to be preferable interms of the yield of FDCA-forming furanics from dehydrating fructosesolutions of varying dry solids concentrations, from 10 weight percentto 20 weight percent to 30 weight percent, with the more dilute fructosesolutions also providing higher yields of the FDCA-forming furanics foran acetic acid/water mixture containing this amount of water. As aconsequence, it will be preferred in many cases to add a significantamount of water in the dehydration step 14 alongside a product,byproduct or process intermediate stream as received from an existing,operating wet or dry grain milling process.

The bromine source for the dehydration step 14 can be any material thatproduces bromide ions or radicals in the reaction mixture, e.g.,hydrogen bromide, hydrobromic acid, sodium bromide, elemental bromine,benzyl bromide, and tetrabromoethane. In an embodiment, the brominesource for the dehydration step 12 is hydrogen bromide, which couldfunction with the feed 12 as an acid catalyst for the dehydration step14 in the form of hydrobromic acid.

The solvent for dehydration step 14 preferably comprises acetic acid ora mixture of acetic acid and water, as FDCA and its derivatives arelargely insoluble in both of acetic acid and water at oxidationtemperatures and as the Mid-Century type oxidations have typically beencarried out in acetic acid. In certain other embodiments, in light ofU.S. Pat. No. 7,985,875 to Hashmi et al. wherein bromine-containingionic liquids such as 1-alkylpyridinium bromides and1,3-dialkylimidazolium bromides are indicated as useful promoters in thepresence of acetic acid and water for a Mid-Century-type oxidation ofp-xylene to provide terephthalic acid, the solvent for the dehydrationstep 14 may additionally comprise such a bromine-containing ionicliquid. In another embodiment, the feed 12 is dehydrated in the furtherpresence of an alcohol having at least one carbon.

A variety of methods have been described for carrying out a dehydrationof hexoses to provide HMF or derivatives of HMF, typically using acidcatalysts, that could be used for accomplishing the dehydration step 14.WO 2013/106136 to Sanborn et al., for example, describes a method forproducing HMF or HMF derivatives (e.g., the ester or ether derivatives)from an aqueous hexose sugar solution in which, according to certainembodiments, the acid-catalyzed dehydration step is conducted with rapidheating of the hexose solution from an ambient to a reactiontemperature, as well as with rapid cooling of the HMF and/or HMFderivative/unconverted sugar mixture prior to the separation of thefermentation-ready residual sugar product from the HMF and/or HMFderivative product. In addition, the time between when the aqueoushexose solution has been introduced into a reactor and the HMF and/orHMF ether products begin to be cooled is preferably limited.

By accepting limited per-pass conversion to HMF, the overall exposure ofthe HMF that is formed from any given aqueous hexose solution to acidic,elevated temperature conditions is limited, and preferably little to nounwanted or unusable byproducts such as humins are produced requiringwaste treatments. Separation and recovery of the products is simplifiedand levels of HMF and other hexose dehydration products known to inhibitethanol production by fermentation are reduced in the residual sugarsproduct to an extent whereby the residual sugars product can be useddirectly for ethanol fermentation if desired. Processes conducted asdescribed were characterized by very high sugar accountabilities andhigh conversion efficiencies, with very low losses of sugars beingapparent.

US 2009/0156841 by Sanborn et al. provides a method of producing HMFand/or HMF esters from a carbohydrate source by contacting thecarbohydrate source with a solid phase acid catalyst. A method ofproducing HMF esters, in one embodiment, involved heating a carbohydratestarting material with a solvent in a column, and continuously flowingthe heated carbohydrate and solvent through a solid phase catalyst inthe presence of an organic acid to form a HMF ester. The HMF esters or amixture of HMF and HMF esters can be oxidized together to provide FDCAin good yields, by combining the HMF ester with an organic acid, cobaltacetate, manganese acetate and sodium bromide in the presence of anoxygen source and at elevated temperatures and pressures.

U.S. Pat. No. 8,558,018 to Sanborn and U.S. Pat. No. 8,519,167 to Muñozde Diego et al. teach methods whereby HMF ether derivatives formed bycarrying out the dehydration in the presence of a C₁-C₅ alcohol can alsobe oxidized alone or in mixtures with HMF to yield FDCA and esterderivatives of FDCA, using the same oxidation catalyst systems andsubstantially the same conditions as used for forming FDCA from HMF, sothat in certain embodiments of the integrated process 10, the feed 12may be dehydrated in the presence of an organic acid or a C₁-C₅ alcoholto provide an oxidation feed 16 including ester or ether derivatives ofHMF or a combination of HMF with ester or ether derivatives of HMF.

Referring back to FIG. 1, the integrated process 10 for producing2,5-furandicarboxylic acid and/or a derivative thereof from a six carbonsugar-containing feed then broadly comprises contacting an oxidationfeed 16 from the dehydration step 14 containing various FDCA-formingfuranics (both newly-generated in the dehydration step 14 and recoveredand recycled from the oxidation step 18) with a metal catalyst and withan oxygen source 28 at an elevated temperature for a time sufficient toproduce an oxidation product mixture comprising 2,5-furandicarboxylicacid (FDCA) and/or a derivative thereof, the solvent, and a residualcatalyst. In an embodiment, the oxidation feed 16 can be combined with asource of oxygen 28 before contacting with the metal catalyst.

The oxidation feed 16 comprising at least one bromine containing speciesprovides some or substantially all of the bromine required for theoxidation step 18. Furthermore, the integrated process 10 may furthercomprise regulating the amount of bromine in the oxidation step 18 byadding to or removing bromine from the oxidation feed 16 prior to theoxidation step 18. Any suitable method can be used to control the amountof bromine in the oxidation feed 16 prior to the oxidation step 18, suchas for example using ion exchange to remove additional Br and recycleHBr after ion exchange to the dehydration step 14.

As disclosed herein above, the bromine containing species may compriseone or more of inorganic bromides such as HBr; metal bromides includingbut not being limited to lithium bromide, sodium bromide, potassiumbromide, magnesium bromide, calcium bromide, cobalt bromide andmanganese bromide; and organic bromides such as, but not being limitedto, 5-(bromomethyl) furfural and derivatives thereof, and brominatedfiiranic oligomers. In an embodiment, a bromine source may be introducedat the oxidation step 18 to supplement the bromine-containing species inthe oxidation feed 16 from the dehydration step 14, so that the relativeamounts of inorganic and organic bromine in the oxidation feed 16 may beregulated, for example, by means of the nature and amounts of thebromine source(s) in the dehydration step 14 and further brominesource(s) at the oxidation step 18. In certain embodiments, thebromine-containing species in the oxidation feed provide substantiallyall of the bromine requirements for a Mid-Century type oxidation processcarried out according to any conventionally known method and using anyof the various so-called metal bromide catalysts described in the art.

Any suitable homogeneous oxidation catalyst can be used which iseffective for converting HMF, HMF esters or HMF ethers in the oxidationfeed (based on the dehydration method used) to FDCA and/or derivativesof FDCA. The metal catalyst may comprise one or more transition metals.In an embodiment, the metal catalyst comprises either or both of Co andMn. In another embodiment, the metal catalyst further comprises Zr orCe. Furthermore, the metal catalyst may react with the bromine presentin the bromine containing species and may form insitu metal bromides. Inan embodiment, the metal catalyst in the oxidation reaction consistsessentially of from 10 to 10000 parts per million or 10 to 8000 partsper million or 59 to 5900 parts per million or 2000 to 4000 parts permillion of Co; from 5 to 10000 parts per million or 55 to 5500 parts permillion or 200 to 1000 parts per million of Mn; and a bromine source inthe oxidation reaction is present in the range of 0.1 to 20000 parts permillion or 203 to 20000 parts per million or 10 to 10000 parts permillion or 1000 to 2000 parts per million of Br.

The homogeneous oxidation catalyst can be selected from a variety ofoxidation catalysts, but is preferably a catalyst based on both cobaltand manganese and suitably containing a source of bromine. Still othermetals have previously been found useful for combining with Co/Mn/Br,for example, Zr and/or Ce (see Partenheimer, Catalysis Today, vol. 23,no. 2, pp 69-158 (1995)), and may be included as well. In an embodiment,the metal catalyst consists essentially of Co, Mn, and Br as disclosedhereinabove and Zr from 5 to 10000 parts per million or 50 to 5000 partsper million or 100 to 1000 parts per million. In an embodiment, themetal catalyst consists essentially of Co, Mn, and Br as disclosedhereinabove and Ce from 1 to 10000 parts per million or 10 to 5000 partsper million or 50 to 1000 parts per million.

Each of the metal components can be provided in any of their known ionicforms. Preferably the metal or metals are in a form that is soluble inthe reaction solvent. Examples of suitable counterions for cobalt andmanganese include, but are not limited to, carbonate, acetate, acetatetetrahydrate and halide, with bromide being the preferred halide. Withacetic acid (or a mixture of acetic acid and water) as the solvent, theacetate forms of Co and Mn are conveniently used.

The oxidation step can be performed at a temperature of from 120 to 250and more particularly 170 to 190 degrees Celsius and at an oxygenpartial pressure of from 0.02 to 100 bar or from 0.02 to 21 bar or from0.2 to 100 bar or 0.2 to 21 bar.

The molar yield of 2,5-furandicarboxylic acid from the oxidation step onthe basis of the FDCA-forming furanics in the oxidation feed is at least60 or 70 or 80 or 90 or 95 percent or any integer percent thereof.

As shown in FIG. 1, the integrated process 10 as disclosed hereinabovealso comprises the step 22 of purifying and separating the mixtureobtained in the oxidation step 18 to obtain FDCA and/or a derivativethereof 24 and recycling 26 at least a portion of the solvent obtainedin the purification step to the dehydration step 14.

Following the oxidation step 18, the FDCA is separated out from thesolvent for further purification, and at least a portion of the solventis recycled via stream 26 as previously mentioned. Since FDCA is largelyinsoluble in acetic acid or in mixtures of acetic acid and water at mildconditions, separation of the FDCA from the preferred solvent is easilyaccomplished by filtration or centrifugation.

Purification methods for the FDCA may include those methods described,for example, in U.S. Pat. No. 8,748,479 to Shaikh et al., U.S. Pat. No.8,791,278 to Shaikh et al. and US 2014/0142328 to Shaikh et al., thoughany suitable method can be used for purifying the diacid, including, butnot limited to crystallization/other methods, prior to conversion of thediacid to other derivatives such as esters and polymers. In U.S. Pat.No. 8,748,479, a crude FDCA product is fed to a crystallization zone,followed by a solid-liquid displacement zone to provide a low impurityslurry stream. The FDCA solids are then dissolved to provide ahydrogenation feed that is then hydrogenated to yield a hydrogenatedFDCA composition. This composition is then routed to a secondcrystallization. A purified wet cake stream containing FDCA is thendried to generate a dry purified FDCA product stream. In U.S. Pat. No.8,791,278, a secondary oxidation zone is utilized in conjunction withcrystallization, and optionally with hydrogenation, to provide a dried,purified FDCA product, whereas in US 2014/0142328, a first lowtemperature oxidative purification is followed by a high temperatureoxidative purification, then by crystallization and drying.

As discussed above, in certain embodiments, a combination of inorganicand organic bromine may desirably be present in the oxidation feed 16.Although not to be bound by any theory, it is believed that the mannerand relatedly the form in which the bromine component is introduced intothe process of sugar dehydration and subsequent oxidation can lead tooverall process synergies. In particular, by introducing a brominesource in the performance of the dehydration step, of another earlierstep or a combination generally of such earlier steps (meaning, inadvance of the oxidation step) whereby a furanic oxidation precursor orprecursors to FDCA or to an FDCA ester product are to be produced forthen being oxidized to FDCA or an FDCA ester product, so that anoxidation feed including the furanic oxidation precursor or precursorsas well as at least one bromine-containing species is produced, at leastequivalent FDCA yields can be achieved with reduced amounts of bromine(as hydrobromic acid) as compared to the circumstance wherein thebromine for the Mid-Century type oxidation is added exclusively at theoxidation step 18 in the form of hydrobromic acid.

The capacity to reduce bromine requirements in the process overall andin the oxidation step in particular can be seen to provide a number ofbenefits and advantages. Reduced bromine in the higher temperatureoxidation step (in the form of hydrogen bromide) can be expected toreduce corrosion in the overall process. Correspondingly, because thebromine is more efficiently used in producing FDCA, improved FDCA yieldsmay in fact be achievable without increasing catalyst requirements andwithout making the conditions of the oxidation reactor more corrosive.

The integrated process as disclosed herein above and below, providesseveral advantages, including, but not limited to, that use of the sameacetic acid or acetic acid and water solvent in the dehydration andoxidation steps enables the use of the more stable AcMF precursor toFDCA, without the need for isolating either HMF or AcMF. Furthermore,the use of common solvent and common bromine source provides an addedadvantage that the solvent, with or without the bromine source, can berecycled at least in part after the oxidation step into the dehydrationstep, thereby resulting in significant cost (capex, operating cost,conversion) reduction in taking a feed comprising a six-carboncontaining species such as a high fructose syrup (e.g., a high fructosecorn syrup) to FDCA. Furthermore, the integrated process of the presentinvention is amenable for retrofitting to existing oxidation assetsand/or existing HFCS assets.

Within the general context of an integrated process having theseadvantages, however, a complication arises in that while the dehydrationstep 14 would preferably (as explained above) make use of a feed 12 thatis fairly dilute, yet the amount of water implicated in feed 12 andgenerated in the dehydration step 14 will be greater than ideal for aMid-Century type oxidation, so that the water content of the oxidationfeed will in preferred embodiments need to be limited. Excessive waterhas in this regard been found to be detrimental to the oxidation step,and limiting the water content in and from the oxidation step will beunderstood as desirable also for improving FDCA recovery viacrystallization, given that FDCA has differing solubilities in mixturesof acetic acid and water with differing amounts of water, see WO2008/054804 to Lilga et al. At the same time, some water content isbeneficial for the oxidation reaction and will be appreciated as helpfulfor heat management in the oxidation. We would prefer that the watercontent in the oxidation reactor should be regulated in the range offrom about 5 to about 7 percent by weight.

The common bromine source and common solvent aspects of the presentinvention enable the regulation of the water content in the steps 14 and18 to the preferred levels in each, as well as the management of thecatalyst and solvent in the process and of heat generated in theoxidation step 18, and it will be well within the capabilities of thoseskilled in the art to determine the design (by composition and volume)of the recycle stream 26 to the dehydration step 14 as well as anyadditional recycle stream (not shown) to the oxidation step 18 or purgesof excess water from the overall process, given the details providedabove.

FIG. 2 schematically depicts an alternative embodiment 30 of anintegrated process according to the present invention, wherein the HMFand/or HMF derivatives produced in the dehydration step 14 arehydrogenated in an hydrogenation step 32 with a source 34 of hydrogen,to provide the reduced derivatives of HMF (furan dimethanol andtetrahydrofuran dimethanol) or of the ester or ether derivatives of HMFand its hydrogenated derivatives. US 2010/0212218 to Gruter, U.S. Pat.No. 8,231,693 to Gruter and U.S. Pat. No. 8,367,851 to Lilga et al, forexample, describe methods for forming these reduced derivatives. In US2010/0212218 and U.S. Pat. No. 8,231,693, the hydrogenation of HMF andHMF ethers, primarily, are respectively described. The reducedderivatives of HMF in US 2010/0212218 are described as stable andindependently useful for fine chemical applications, as a pharmaceuticalintermediate, in fuels or for oxidation to provide FDCA. U.S. Pat. No.8,231,693 indicates that the hydrogenation of HMF ether derivativesproduces materials useful as fuels and fuel additives, as well asindicating that the reduced HMF ethers may likewise be oxidized toprovide FDCA using the same Mid-Century type oxidation methods andcatalysts as useful for the conversion of HMF and/or of HMF ethers toFDCA. U.S. Pat. No. 8,367,851 to Lilga et al. for its part relates thatfurandimethanol and tetrahydrofuran dimethanol also have application inadhesives, sealants, composites, coatings, binders, foams, curatives,polymers, solvents, resins and as monomers.

Because the hydrogenation of HMF and/or of the derivatives of HMFproduced in the dehydration step 14 thus provides materials having otherpossible end uses and applications, in an alternative embodiment 40shown schematically in FIG. 3, a portion 16 a of the HMF and/or HMFderivatives from dehydration step 14 is hydrogenated in hydrogenationstep 32 to provide one or more reduced derivatives of HMF and/or of thederivatives of HMF from dehydration step 14 in a product stream 36,while a remaining portion 16 b is directly oxidized in oxidation step 18as in FIG. 1. Optionally, a portion 38 of the reduced derivatives fromhydrogenation step 34 may also be oxidized in oxidation step 18 toprovide FDCA.

FIG. 4 schematically illustrates another co-product scenario 50, whereinan etherification step 42 is performed on a portion 36 a of the reducedderivatives of HMF and/or of the derivatives of HMF from dehydrationstep 14 to produce etherified reduced derivatives of HMF as additionalco-products (additional to the reduced products in stream 36) in productstream 44 (though a portion 44 a may optionally be oxidized as shown inFIG. 4 in oxidation step 18 to produce FDCA, consistent with U.S. Pat.No. 8,231,693 to Gruter wherein the reduced ether derivatives of HMF aredescribed as suitable for preparing FDCA by oxidation). Thus, inInternational Patent Application No. PCT/US2014/070021 filed Dec. 12,2014 for “Mono- and Dialkyl Ethers of Furan-2,5-Dimethanol and(Tetrahydrofuran-2,5-Diyl) Dimethanol and Amphiphilic DerivativesThereof”, and claiming the benefit of U.S. Ser. No. 61/918,239 filedDec. 19, 2013, a method is described for the etherification of furandimethanol and tetrahydrofuran dimethanol from the hydrogenation of HMF,and for the preparation of amphiphilic derivatives thereof for use assurfactants and dispersants. More particularly, a process is describedfor preparing linear mono- and di-alkyl ethers of furan dimethanoland/or of tetrahydrofuran dimethanol which comprises contacting eitherFDM or THF dimethanol in a polar aprotic organic solvent with apermittivity (ε) >8, at a temperature ranging from −25° C. to 100° C.,with either a) an unhindered Brønsted base having a difference in pKa(ΔpKa) ≥15 relative to the pKa of a hydroxyl group of either said FDM orbHMTHF, or b) a hindered Brønsted base and a nucleophile. An alternativemethod for forming the mono- or dialkyl ethers of FDM and/or THFdimethanol is described in U.S. Provisional Patent Application No.62/093,730, filed Dec. 18, 2014 for “CO₂-Mediated Etherification ofBio-Based Diols”, and involves contacting the FDM or TI-F dimethanolwith an alkylating agent in an alcoholic solvent, in the presence of acatalyst that generates in situ a weak acid, at a temperature for asufficient time to convert the diol to a corresponding alkyl ether. Theweak acid is preferably carbonic acid that is formed in situ fromhydrated carbon dioxide (CO₂) catalyst, and that disappears afterdepressurization of the reaction. The resulting mono- and dialkyl ethersare indicated as useful biobased replacements for the glycol ethers madecommercially from non-renewable resources, as well as for the productionof polyethers and epoxides. And, as already mentioned above, U.S. Pat.No. 8,231,693 to Gruter indicates that the etherification and reductionof HMF will produce materials in product stream 44 that would also beuseful as fuels or fuel additives.

Turning now to FIG. 5, a process is schematically shown for makingfurther products from the FDCA and/or a derivative of FDCA from anintegrated process as shown in FIG. 1, though it will of course beunderstood that the further products may be equally made from the FDCAproduced according to any of the other embodiments schematically shownin FIGS. 2-4.

Thus, in one embodiment of a further process step 52, an esterificationcan be carried out on the FDCA with a C₁-C₁₂ aliphatic alcohol or aC₁-C₁₂ aliphatic diol, under conditions effective for carrying out theesterification and optionally in the presence of a suitableesterification catalyst to prepare monoalkyl and dialkylfuran-2,5-dicarboxylates for subsequent use in polyesters andcopolyesters. One such esterification method is described in U.S. Pat.No. 8,859,788 to Partin et al., wherein a purified FDCA solid product ina dried solid form or as a wet cake FDCA composition is fed to anesterification reactor; a liquid reaction mixture is provided in theesterification reactor which comprises FDCA, an alcohol compound,dialkyl furan-2,5-dicarboxylate, water and5-(alkoxycarbonyl)furan-2-carboxylic acid; an esterification reaction iscarried out in the liquid reaction mixture in the presence of thealcohol; passing at least a portion of the vapor in the vapor space,comprising dialkyl furan-2,5-dicarboxylate, unreacted alcohol,5-(alkoxycarbonyl)furan-2-carboxylic acid and water, into arectification zone in which at least a portion of the5-(alkoxycarbonyl)furan-2-carboxylic acid is converted to a liquid phasecondensate; contacting at least a portion of the liquid phase condensatewith the liquid reaction mixture; and continuously discharging from therectification zone a dialkyl furan-2,5-dicarboxylate vapor compositioncomprising dialkyl furan-2,5-dicarboxylate, water, unreacted alcohol andby-products. Another esterification method is described in WO2014/099438 to Stensrud et al., wherein FDCA is reacted in a liquidreaction system with an alcohol in a CO₂-predominant atmosphere withoutthe presence of any other acid catalyst, under conditions correspondingto either supercritical, critical or near-critical temperatures andpressures for the alcohol species and/or CO₂ gas. In a variation, theresultant first ester mixture is reacted with a second alcohol in atransesterification reaction to regenerate the first alcohol. WO2014/070415 to Stensrud et al. relates to still another method, for thealcohol-mediated esterification of FDCA with carbonates, wherein FDCA isreacted with a dialkylcarbonate in the presence of an alcohol-containingsolvent and without either an extrinsic acidic or basic catalystspecies.

In other embodiments of further processing signified by step 52, theFDCA may be used to prepare a prepolymer or polymer such as a polyesterby transesterification of ester derivatives of 2,5-furandicarboxylicacid with a C₂ to C₁₂ aliphatic diol or a polyol and optionally at leastone of a polyalkylene ether glycol (PAEG), a polyfunctional acid or apolyfunctional hydroxyl acid. For example, the FDCA may be used in themanufacture of a polyester as described, for example, in any of US2014/0205786 to Nederberg et al. (comprising poly(trimethylenefurandicarboxylate) from FDCA and 1,3-propanediol); U.S. Pat. No.6,140,422 to Khanarian et al.; U.S. Pat. No. 5,959,066 to Charbonneau etal.; U.S. Pat. No. 8,420,769 to Eritate; US 2011/0282020 to Sipos; U.S.Pat. No. 8,143,355 to Matsuda et al.; U.S. Pat. No. 2,551,731 to Drewittet al.; “New biobased polyester fiber”, Chemical Fibers InternationalJanuary 2014 (describing a polyester made with FDCA and monoethyleneglycol (PEF)); and JP 2009001630 to Eritate (describing polymers withpolyester or polyamide groups whose ester or amide groups are bonded tofuran rings and which polyester or polyamide block segments are joinedvia siloxane groups). The FDCA may also be used to manufacture apolyamide as described, for example, in any of US 2015/0044927 to Chanet al. (describing a polymer derived from an aromatic diamine comprisingm-phenylene diamine and an aromatic diacid or derivative thereof,especially FDCA or a derivative thereof); WO 2014/012829 to Jeol et al.;US 2014/0135449 to Jeol; and CN 10285054. The integrated process mayfurther comprise the steps of preparing a semi-crystalline prepolymer ofisoidide with a 2,5-furandicarboxylic acid ester and optionally1,4-butanediol or 2,3-butanediol by melt polymerization, then performingsolid state post condensation on the semi-crystalline prepolymer.

The integrated process may further comprise preparing a furan basedpolyamide compositions comprising contacting an aliphatic or aromaticdiamine with 2,5-furandicarboxylic acid and/or derivatives thereof,optionally in the presence of a solvent.

The integrated process may further comprise the steps of a) dissolvingan aromatic diamine monomer in a polar solvent to form a diaminesolution under inert atmosphere, wherein the solvent is selected fromthe group consisting of dimethyl acetamide, dimethyl formamide anddimethyl sulfoxide, and wherein the aromatic diamine comprisesm-phenylene diamine; b) adding an aromatic diacid monomer or aromaticdiacid derivative component in the form of 2,5-furandicarboxylic acidfrom the process of Claim 1 or a derivative thereof to the diaminesolution at a temperature in the range of −5 to 35 degrees Celsius toform a reaction mixture; c) continuing the reaction until there is nofurther increase in temperature or until a desired viscosity of thereaction mixture is achieved; and d) isolating the polymer from thereaction mixture.

The integrated process as disclosed hereinabove can be operated in anysuitable configuration/mode such as, batch, continuous and semi batchprocess.

The present invention is more particularly illustrated by the exampleswhich follow:

EXAMPLES

The methods disclosed herein are illustrated in the following examples.From the above discussion and these examples, one skilled in the art canascertain the essential characteristics of this invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various uses andconditions.

All commercial reagents were used as received. ACS grade glacial aceticacid was obtained from Fisher Scientific. All other chemicals wereobtained from Sigma-Aldrich (St. Louis, Mo.) unless stated otherwise.Purified 5-(hydroxymethyl)furfural and 5-(acetoxymethyl)furfural asreceived for use in the oxidation reactions from Archer Daniels MidlandCompany for certain oxidation feeds (OF-c, OF-d and OF-e in Table 2below) were synthesized and purified as more particularly describedhereafter. 2,5-furan dicarboxylic acid (2,5-FDCA) was obtained fromSarchem Laboratories (Farmingdale, N.J.) in >99% purity. Oxidationintermediates, 2,5-diformylfuran and 5-formyl-2-furancarboxlyic acid,were purchased in >98.0% purity from Tokyo Chemical Industry, Co forquantification.

The following abbreviations are or may be used in the examples: “° C.”means degrees Celsius “RPM” means revolutions per minute; “wt %” meansweight percent, “g” means gram, “min” means minute(s), “μL” meansmicroliter; “ppm” means microgram per gram, “μm” means micrometer; “mL”means milliliter; “mm” means millimeter and “mL/min” means milliliterper minute; “sccm” means standard cubic centimeters per minute, “DMF”means N,N-Dimethylformamide, “HMF” means 5-(hydroxymethyl)furfural,“AcMF” means 5-(acetoxymethyl)furfural, “DFF” means 2,5-Diformylfuran(known also as 2,5-furandicarbaldehyde), “FFCA” means5-formyl-2-furancarboxlyic acid, “FDCA” means 2,5-furandicarboxylicacid, “OBMF” means 5,5′(oxy-bis(methylene))bis-2-furfural, “Co” meansCobalt, “Mn” means Manganese, “Ti” means Titanium, “Zr” means Zirconium.

General Methods

HPLC Analysis of HMF/AcMF Present in the Oxidation Feed

HPLC analysis was used as one means to quantify yield of oxidationproducts and conversion of starting materials, and was used to analyzesamples containing HMF, AcMF, OBMF, DFF, FFCA, and FDCA before and afterreaction. An Agilent 1200 series HPLC equipped with a Zorbax SB-aqcolumn (4.6 mm×250 mm, 5 μm) and photodiode array detector was used forthe analysis of the reaction samples. The wavelength used to monitor thereaction was 280 nm.

The HPLC separation of HMF, DFF, FFCA, and FDCA was achieved using anisocratic method with a 1.0 mL/min flow rate of a mobile phasecomprising 0.5% v/v trifluoroacetic acid (TFA) in water and a runduration of 30 minutes. The HPLC separation of AcMF and OBMF wasachieved using a gradient method with a 1.0 mL/min flow rate combiningtwo mobile phases: Mobile Phase A: 0.5% v/v TFA in water and MobilePhase B: acetonitrile. In both isocratic and gradient methods, thecolumn was held at 60° C. and 2 μL injections of samples were performed.Analyzed samples were diluted to <0.1 wt % for components of interest ina 50:50 (v/v) acetonitrile/water solvent. The solvent composition andflow rates used for the gradient method is given in Table 1 with linearchanges occurring over the corresponding step whenever the compositionchanges.

TABLE 1 Gradient program for HPLC Volume % Mobile Volume % Mobile Starttime Phase B, at Beginning Phase B, at End of Step (min) of Step Step 10.0 0 0 2 6.0 0 80 3 20.0 80 80 4 25.0 80 0 5 25.1 0 0 6 30.0 0 0

Retention times were obtained by injecting analytical standards of eachcomponent onto the HPLC. The amount of the analyte in weight percent wastypically determined by injection of two or more injections from a givenprepared solution and averaging the area measured for the componentusing the OpenLAB CDS C.01.05 software. The solution analyzed by HPLCwas generated by dilution of a measured mass of the oxidation feedsolution, oxidation reaction solution, oxidation reaction solids, oroxidation reactor washings with a quantified mass of 50:50 (v/v)acetonitrile/water solvent. Quantification was performed by comparingthe areas determined in the OpenLAB software to a linear externalcalibration curve generated at five or more starting materialconcentrations. Typical R² values for the fit of such linear calibrationcurves was in excess of 0.9997.

While the presented HPLC method was used for this analysis, it should beunderstood that any HPLC method that can discriminate between FDCA,starting materials, intermediates, impurities, and solvent can be usedfor this analysis. It should also be understood that while HPLC was usedas a method of analysis in this work, other techniques such as gaschromatography could also be optionally used for quantification whenemploying appropriate derivatization and calibration as necessary.

LAB Color Measurements

A Hunterlab ColorQuest Spectrocolorimeter (Reston, Va.) was used tomeasure the 2,5-FDCA color. Color numbers are measured as APHA values(Platinum-Cobalt System) according to ASTM D-1209. The “b*” color of2,5-FDCA is calculated from the UV/VIS spectra and computed by theinstrument. Color is commonly expressed in terms of Hunter numbers whichcorrespond to the lightness or darkness (“L”) of a sample, the colorvalue (“a*”) on a red-green scale, and the color value (“b*”) on ayellow-blue scale. In the context of this invention, the “b*” colorvalue is preferably near 0.

Characterization of the Bromine Source in the Bromine Containing Species

The total content of bromine in the oxidation feeds (“Crude Furanics inAcetic Acid”; OF-1 to OF-4) was measured by ICP-MS on a Thermo Element 2HR-ICP-MS. Ion chromatography measurements were performed using a DionexICS-3000 instrument.

The form of the bromine containing species may be characterized bymethods such as ICP-MS and Ion Chromatography (IC). Since IC may be usedto characterize bromine in an ionic form and ICP-MS provides ameasurement of total amount of bromine, it was assumed that thedifference between ICP-MS and IC was the amount of covalently boundbromine, which will not be detected in IC. The covalently bound brominecould either be bound to the catalyst metal or bound to organicmaterials in the oxidation feed.

IC of oxidation feeds was carried out by diluting a sample of anoxidation feed mixture in methylene chloride. Water soluble, ionicbromine was then extracted out using water in a bi-phasic partitioning.A sample of the water phase was then analyzed by IC. This procedure wasverified by quantitatively recovering an ionic Br standard by extractionas well. Extraction of the crude oxidation feed liquid was used tominimize precipitation of humins in the water phase and prevent solubleorganics from damaging the IC system. IC of oxidation reaction productliquids was carried out by dilution in water and injection for analysisusing a Dionex AS17 column.

Examples 1-4: Integrated Production of FDCA in Acetic Acid as Solvent

The integrated process of making FDCA as disclosed herein belowcomprises the first step (1A) of dehydrating a sugar feed to produce anoxidation feed, with concentrating the crude feed without purificationexcept filtration and followed by the step of oxidation of theas-produced oxidation feed to FDCA.

Step 1A: Production of Crude Oxidation Feed in Acetic Acid (OF-1 toOF-4)

Several oxidation feeds were generated first by combining glacial aceticacid (1182 g, 19.68 mol), aqueous hydrobromic acid solution (at an HBrconcentration of 48 wt. % in water; 16.97 g. 0.101 mol), and a mixedfructose/glucose syrup (in a 97/3 ratio by weight of fructose toglucose, 76.88% dry solids basis in water, 1203 g) in a 2 liter Wheatonbottle. These materials were mixed at ambient temperature on a drumroller until homogeneous, then degassed in a sonicator. Theconcentration of the HBr relative to fructose and glucose was keptconstant at 1.99% mol based on HPLC analysis of the feed.

The sugar, acid and water feed solution was then pumped using a 500cubic centimeter dual piston ISCO pump at a flow rate of 0.55 mL/mininto a 66 cm×1.27 cm tubular titanium reactor with a total volume of 62cubic centimeters. The reactor was packed with solid 3 mm glass beads,and had a void volume of 23 cubic centimeters. The reactor was outfittedwith four internal thermocouples and a hot oil jacket for heating andtemperature control. The reactor effluent tubing was outfitted with atitanium PTFE/fiberglass diaphragm back pressure regulator and digitalpressure sensor to control reactor pressure.

A second 1000 cubic centimeter dual piston ISCO pump was teed into thereactor influent and used to pump pure glacial acetic acid at a flowrate of 1.55 mL/min to produce a total flow rate through the reactor of2.10 mL/min and a 9.96 min residence time. The final concentration ofthe total dry solids, fructose, glucose and water in the reactor basedon flow rates of the pumps, densities of the solutions and analysis ofthe HFCS was: 11.2%/o wt, 10.7% wt, 0.3% wt and 3.4% wt respectively.Flow was established through the reactor and back pressure was appliedat 100 psi using the regulator. Once flow was re-established the hot oiltemperature was set to 160 C and the reactor was brought to temperature.After the reactor temperature equilibrated, the experiment was run forapproximately 5.08 hrs and sampled four times intermittently.

These four samples were prepared and analyzed for furanic componentsusing a Phenomenex PFP analytical column (150 mm×2.1 mm×1.7 um) on aWaters Acquity UPLC equipped with a diode array detector (280 nm) andsingle quad mass spectrometer (ES+). Residual fructose and glucose weredetermined through derivatization with pyridine containingO-methylhydroxylamine hydrochloride and acetic anhydride at 80 degreesCelsius, with subsequent analysis using a J&W DB-5 MS UI column(30m×0.25 mm×0.25 um) on an Agilent 7890 equipped with an FID detector.Water content of the four samples was determined using a Mettler Toledovolumetric Karl Fischer auto-titrator.

The mole yield of furanic oxidation precursors to FDCA—namely, HMF, AcMFand HMF dimer—relative to the total sugar in the feed, and theconversion of fructose and glucose were calculated for each sample, thenaveraged and measured for standard deviation. Mole yields for thesamples ranged from 54.7% to 57.6%, with an average of 56.4% and astandard deviation of 1.2%. Fructose conversions ranged from 97.7% to98.1%, with an average of 97.9%. The glucose conversions ranged from44.6% to 46.3%, with an average of 45.2%. Fructose and glucoseconversions resulted in a total average conversion of 96.2%, with astandard deviation of 0.20%. No insolubles were observed in any of thesamples.

Concentration of the Effluent from the Dehydration Step 1A to obtain theOxidation Feed

Oxidation feeds generated by dehydration of a 10 wt % sugar feed (97/3fructose/glucose), according to procedures outlined in Step 1A,contained 4-5 wt % combined HMF and AcMF concentrations, as measured byHPLC. Therefore, effluent from the dehydration reactor was concentratedby a factor of approximately 4-6 by rotary evaporation, removing aportion of the acetic acid and water in the mixture. Concentration wasperformed at a temperature of 25-30° C. and an absolute pressure of 5-15torr. The resulting mixtures are characterized in Table 2.

Table 2 summarizes the composition of the as-produced oxidation feeds(“Crude Furanics in Acetic Acid”) after concentration, including thestarting concentrations of FDCA-forming furanics, defined as AcMF, HMF,and OBMF. These components are defined as “FDCA-forming” since they aredirectly presumed to form FDCA throughout the course of oxidation.Entries OF-1 through OF-4 of Table 2 include “Crude Furanics in AceticAcid”. While the crude oxidation feeds were each filtered through a 2.0μm HPLC filter prior to oxidation, unless otherwise noted herein, noadditional purification was performed to remove unreacted sugars,humins, levulinic acid, or non-FDCA forming furanics (furfural,2-(hydroxyacetyl)furan, and 2-(acetoxyacetyl)furan).

These oxidation feeds OF-1 through OF-4 were then oxidized underdifferent sets of conditions as described in Step 1B below, to provideExamples 1-4 of the present invention.

TABLE 2 Summary of Major Oxidation Feed Components Amount and Source ofBromine Bromine Bromine FDCA-Forming Furanics present from Added asFuranics/Br in Oxidation Feed^(a) Dehydration/ HBr in Total Ratio inOxidation Feed (OF) HMF AcMF OBMF Water Concentration Water Br FeedEntry Description: (wt %) (wt %) (wt %) (wt %) (ppm) (ppm) (ppm)(mol/mol) OF-1 Crude Furanics in 5.5 13.3 0.2  1.8^(c) 3800^(d) —3800^(d) 26 Acetic Acid-1 OF-2 Crude Furanics in 7.0 15.3 0.2  2.4^(c)5500^(d) — 5500^(d) 21 Acetic Acid-2 OF-3 Crude Furanics in 10.4 16.80.3  1.7^(c) 5600^(d) — 5600^(d) 26 Acetic Acid-3 OF-4 Crude Furanics in9.0 18.6 0.3  1.4^(c) 4900^(d) — 4900^(d) 30 Acetic Acid-4 OF-a CrudeHMF in 46.3 — 0.1 37^(c) — — — — Water OF-b Crude HMF in 45.4^(b) —0.1^(b) 38^(b) — 9500^(b) 9500^(b) 30 Water with HBr OF-c PurifiedFuranics in 9.8 14.9 — <1^(b) — — — — Acetic Acid OF-d Purified Furanicsin 9.9 15.0 —  1.7^(b) — 5400^(b) 5400^(b) 25 Acetic Acid with HBr OF-ePurified Furanics in 9.9 14.8 — 20^(b) — — — — Acetic Acid with Sugars^(a)Measured by HPLC; ^(b)Calculated based on quantities of measuredmaterials; ^(c)Measured by Karl Fischer Titration; ^(d)Measured byICP-MS

Step 1B: Production of FDCA Using the Oxidation Feeds of Step 1A

A solution with 140 mL acetic acid, 7.7 mL H₂O (5 wt % of solution), anddissolved catalyst (cobalt fed as cobalt (II) acetate tetrahydrate,manganese fed as manganese (II) acetate tetrahydrate, HBr (48 wt %concentration in water), and optionally zirconium added as a zirconiumacetate solution in acetic acid (Sigma Aldrich, USA—413801)) was addedto a 300 mL titanium (Grade 4) Parr autoclave reactor. The amount ofcatalyst (Co, Mn, Br, or, optionally, Zr) in Table 4 was calculated asbelow:

${{AmountofCatalyst}({ppm})} = {\frac{\begin{matrix}{{amountofcatalyst}\left( {{Co},{Mn},{Br},{{or}\mspace{14mu} {Zr}}} \right)} \\({grams})\end{matrix}}{{totalamountofsolution}({grams})} \times 1\text{,}000\text{,}000}$

wherein the amount of catalyst (grams) includes solely the amount ofmetal content, Co, Mn, or Zr, and not the mass of the complexes, such asCo(II) acetate; and the amount of bromine and not the entire mass of thebromine source.

The reactor was then assembled and pressurized to −5.5 bar with airafter leak testing. The reactor was then heated to the indicatedtemperature in Table 4 with 1200 RPM stirring. Once at temperature, thepressure of the reactor was increased to 30 barg with air and acontinuous air flow of 600 sccm initiated. Reactor pressure wasmaintained with a Mity Mite back-pressure regulator on the outlet vaporstream. After the temperature stabilized at the set point, thefuranics-containing oxidation feed was introduced at desired rates withthe aid of a Scientific Systems, Inc. (SSI) HPLC pump. While the vaporphase was continuously flowing, the liquid phase portion of the reactorwas run in a semi-batch configuration wherein the liquid accumulatedthroughout the course of the run.

After approximately 45 minutes, the furanics-containing oxidation feedand air flows were terminated and the reactor was held in batch mode attemperature for an additional 15 minutes. The total mass of liquid feedadded throughout the course of the run was recorded. At the end of thebatch period, the reactor was quenched with cooling water,depressurized, and disassembled. Typically, an FDCA-containing slurryobtained from the reactor was weighed and filtered Both the isolatedsolids and the liquid were analyzed by HPLC. The reactor was then washedwith DMF to recover any remaining solids, and the resulting liquid wasalso analyzed by HPLC. Molar conversion was calculated as the ratio ofmoles of converted FDCA-forming furanics over the total amount ofFDCA-forming furanics fed during the course of a run. Yield of eachcomponent was calculated as a ratio of the moles of component producedto the theoretical number of moles of component possible given theoxidation feed's FDCA-forming furanics content

The results in Table 4 for Examples 1-4 demonstrate a variety ofreaction conditions with the feeds described in Table 2. Since the massof the feed liquid fed throughout the course of a typical semi-batch runin Examples 1-4 ranged from 12.9-13.8 g and the reactor initiallycontained approximately 156-157 g of acetic acid solution, the brominein the feed was substantially diluted once in the reactor. It shouldalso be noted to here that flow rates below the HPLC pump setpoint of0.30 mL/min were observed due to the heightened viscosity of the feedsin Examples 1-4. The final bromine concentration in the reactor at theend of a run was approximated using the initial mass, feed mass, andfinal reactor slurry mass using the following calculation: calculatedfinal Br in reactor (ppm)−(initial reactor solution mass*initial Brconcentration (ppm)+feed solution mass*feed solution Br concentration(ppm))/final reaction slurry mass

Examples 1.1, 1.2, and 1.3 have feeds that span a variety ofcompositions with respect to both HMF and AcMF and effectivelydemonstrate the ability of the at least one bromine containing species(see Table 2) present in the oxidation feed to effectively catalyze theoxidation reaction, with conversion in excess of 99% with observableproducts consisting almost exclusively of FDCA, as shown in Table 4.

Examples 2.1 and 2.2 demonstrate that yields similar to that shown inExample 1 can be maintained due to the presence of at least one brominecontaining species in the oxidation feed at elevated temperature and atdifferent Co and Mn loadings.

Examples 3.1-3.3 were performed at an elevated temperature and withadditional bromine added in the reactor, which also provided high yieldsto FDCA when comparing to Examples 2.1 and 2.2.

Examples 4.1 and 4.2 demonstrate that zirconium may also be used as aco-catalyst for oxidation with potentially beneficial results. In thiscase, addition of 10 mol % Zr with respect to Co was used, providinghigh yields to FDCA with two separate feed sources.

Characterization of the Bromine Containing Species in Examples 1 and 3

Characterization of Oxidation Feed OF-2 in Table 2 showed a totalbromine concentration of 5500 ppm by ICP-MS, of which 2500 ppm waspresent in an ionic form detectable by IC, therefore implying that theremaining 3000 ppm of the bromine containing species in this oxidationfeed were determined to be covalently bound, presumably as5-(bromomethyl)furfural, brominated humins, and other brominatedorganics. Results for characterization of feed OF-3 and the reactionliquids after reaction for Examples 1.3 and 3.2 are also shown in Table3.

TABLE 3 Characterization of Bromine Containing Species in OxidationFeeds and Post-Reaction Acetic Acid Solution Total Ionic Bromine BromineCovalently Measured Measured Bound Bromine by ICP-MS by IC Determined bySample (ppm) (ppm) Difference (ppm) Oxidation Feed OF-2 5500 2500 3000before Oxidation OF-3 5600 2400 3200 Step Sample from Ex. 1.3 520 390130 Reactor after Ex. 3.2 1230 850 380 Oxidation Step

TABLE 4 Oxidation Reactions with Crude and Purified Oxidation FeedsOxidation Reaction Conditions: Oxidation feed rate - 0.12-0.3 mL/min,pressure - 30 barg, oxidant - air, oxidant flow rate: 600 sccm,agitation - 1200 RPM, initial water concentration - 5 wt %, initialcatalyst concentration: shown, initial acetic acid amount - 140 mL,liquid feed duration - 45 min, batch post-oxidation duration - 15 min.Calculated FDCA- Final Feed forming Initial Catalyst BromineConversion/Product Yield Oxi- Rate Furanics in Reactor in Reactor Con-DFF FFCA FDCA dation (mL/ Fed Temp Co Mn Br Zr Br version Yield YieldYield Ex. Feed min) (mmol) (° C.) (ppm) (ppm) (ppm) (ppm) (ppm) (%) (%)(%) (%) 1.1^(a) OF-1 0.3 16 170 2000 100 0 0 ~350 99 (1) <0.1 2 (1) 83(3) 1.2 OF-2 0.3 18.6 170 2000 100 0 0 430 99.7 0.2 2 94 1.3^(a) OF-30.3 24.7 (1.7) 170 2000 100 0 0 470 (10)  99.9 (0.1) <0.1 1 (1) 87 (3)2.1 OF-2 0.3 19.6 200 2200 130 0 0 470 99.8 0.3 2 92 2.2 OF-3 0.3 24.6200 2200 130 0 0 470 99.7 0.2 1 86 3.1 OF-2 0.3 20.2 200 2200 130 890 01320 99.6 0.6 4 91 3.2^(a) OF-3 0.3 24.1 (0.3) 200 2200 130 890 0 1310(20)  99.6 (0.2) <0.1  1 (<1)  92 (<1) 3.3 OF-4 0.3 24.6 200 2200 130890 0 1270 99.8 <0.1 1 91 4.1 OF-2 0.3 20.2 200 2200 130 890 340 133099.5 0.1 1 95 4.2 OF-3 0.3 24.3 200 2200 130 890 340 1320 99.4 0.2 1 89Comparative Example A A.1^(a) OF-a 0.3  56.1 (<0.1) 170 2000 100 370 0360 (<10)  99.7 (<0.1) 9 (3) 18 (1) 54 (6) A.2^(a) OF-a 0.12 22.3 (0.2)170 2000 100 370 0 370 (<10) 99.6 (0.3) <0.1  1 (<1) 81 (4) A.3^(a) OF-b0.12 23.2 (0.3) 170 2000 100 0 0 390 (<10) 99.7 (0.3) <0.1 1 (1) 76 (5)A.4^(b) OF-a 0.3 54.1 (1.7) 200 2200 130 890 0 850 (<10) 99.7 (0.1) 0.9(0.2)  3 (<1) 82 (5) Comparative Example B B.1^(a) OF-d 0.3 25.8 (0.6)170 2000 100 0 0 500 (10)  >99.9 <0.1 0.2 (0.1) 68 (3) B.2^(a) OF-c 0.3 24.7 (<0.1) 200 2200 130 890 0 860 (<10) 99.8 (0.2) <0.1 0.5 (0.1)  72(<1) B.3^(a) OF-e 0.3 25.2 (0.4) 200 2200 130 890 0 850 (<10) 99.4 (0.1)<0.1  0.3 (<0.1) 72 (1) Table Notes: ^(a)Given value for these runs isaverage of two runs with standard deviations shown in parentheses.;^(b)Given value for these runs is average of three runs with standarddeviations shown in parentheses.

Comparative Example A: Production of FDCA Using Aqueous-Based HMFFeedstock

Step AA: Production of Crude Oxidation Feed in Water (OF-a & OF-b)

For comparison, oxidation feeds OF-a and OF-b were generated in theabsence of a bromine source during the dehydration, by direct steaminjection heating in a stainless steel tubular reactor of a 15% drysolids solution of 90 percent fructose in water with 0.5 weight percentof sulfuric acid as the catalyst, consistent with Examples 27-32 of US2014/0315262 to Sanborn et al. More particularly, the mixture was steaminjected with 350 psi steam and under a 175 psi system back pressure toa control temperature of 185 degrees Celsius. The residence time was 4minutes, and produced a dehydration product mixture with 11% final drysolids. The dehydration product mixture was then twice filtered toremove insoluble solids, and purified by adsorbing the HMF onto aHypersol-Macronet® MN270 divinylbenzene-crosslinked macroporouspolystyrene resin (Purolite Corporation, Bala Cynwyd, Pa.) withsubsequent desorption with acetone. After stripping off the acetone bypot distilling under vacuum at about 50 degrees Celsius, a material wasproduced containing about 45 to 50 percent HIMF, less than 0.5 percentof acetone and less than 1 percent residual sugars. This material wasused as is for oxidation feed OF-a, while oxidation feed OF-b wasgenerated by adding in 9500 parts per million of bromine in the form ofa 48 wt. % solution of HBr in water.

Crude “HMF” feeds (OF-a and OF-b) contained crudely purified products ofsugar dehydration in a predominantly water solvent without anysignificant amounts of residual acid. These feeds also contained somesmall amount of humins, residual sugars, levulinic acid, and non-FDCAforming furanics. The oxidation feed OF-b, “Crude HMF in water withHBr,” was generated by addition of 48 wt % HBr in water to a feedcontaining “Crude HMF” (OF-a) to generate a mixture with 9500 ppm Br.While the concentration of Br was higher in this comparative oxidationfeed than in the exemplary oxidation feeds (OF-1 to OF-4), the HMFconcentration was also equivalently higher; therefore, the furanics:Brratio in the oxidation feed (defined as the moles of FDCA-formingfuranics divided by the moles of Br) was consistent with entries OF-1-4of Table 2. In cases where Br was added as HBr, the quantity of Br inthe oxidation feed was quantified by the amount of the HBr added.

Step AB: Production of FDCA Using the Oxidation Feed of Step AA

A procedure similar to that described in step 1B was used except thatthe oxidation feeds of Step AA were used Several reactions with crudeHMF feeds in water with bromine (OF-b) or without bromine (OF-a) aresummarized with process conditions in Table 4.

Example A.1 and A.2 include an approximately equivalent level of bromineinitially in the reactor to that which would be encountered duringExample 1 and 2. Example A.1 in Table 4 shows that substantiallydiminished yields of FDCA are observed at equivalent volumetric flowrates compared to Example 1.3.

Examples A.2 and A.3 in Table 4 are run at lower volumetric flow ratesto better match the equivalent molar flow rates of FDCA-forming furanicsin Example 1 (see column for “FDCA-forming Furanics Fed”). In ExampleA.2, bromine is initially in the reactor and the lower feed rate leadsto a higher FDCA yield than Example A.1 and a diminished amount ofreaction intermediates (DFF and FFCA). However, FDCA yields are stilllower than Example 1.3. In Example A.3, HBr is mixed with the oxidationfeed (OF-b) to provide a final reactor bromine concentration of 390 ppmin a Br introduction scheme similar to Examples 1 and 2, but the FDCAyields are substantially lower.

Finally, Example A.4 provides a comparison to Example 3.2 at comparablevolumetric flow rates and demonstrates that the yield to FDCA is higherusing an integrated processing scheme wherein the oxidation is performedusing the reactor effluent from sugar dehydration in acetic acid withHBr.

Comparative Example B: Production of FDCA in Acetic Acid as SolventUsing Purified Oxidation Feed with HBr

Step BA: Production of Purified Oxidation Feed in Water (OF-c to OF-e)

Oxidation feeds OF-c, OF-d and OF-e were generated by first furtherpurifying additional HMF obtained in the same manner of OF-a (in theabsence of a bromine source), in part through using vacuum distillationwith a 30 cc Vigreux column (3-4 theoretical plates). Analysis of thevacuum distilled HMF material by gas chromatography, HPLC and NMR showeda purity of between 95 and 96 percent. AcMF was synthesized from aportion of this HMF by reaction with acetic anhydride in acetic acid.NMR analysis confirmed quantitative conversion to AcMF. Excess aceticacid was evaporated off, and the vacuum distilled HMF and AcMF werefurther purified by crystallization with diethyl ether before beingcombined with optionally HBr or sugars (as shown in Table 2) and withglacial acetic acid and optionally water to generate comparativeoxidation feeds OF-c, OF-d and OF-e from the further purified furanicmaterials that were initially generated in the manner of OF-a.

Comparative oxidation feeds with “Purified furanics” (OF-c to OF-e) weregenerated by taking pure HMF, AcMF, and optionally HBr or sugars andmixing them with glacial acetic acid and optionally water.

The oxidation feed shown in Table 2, entry OF-d provides a comparison tothe concentrations of FDCA-forming furanics and Br typical for thecrude, concentrated to integrated process feeds in entries OF-1-4 ofTable 2. In the case where Br was added as HBr, the quantity of Br wasquantified using the amount of the material added to the purified feed,which was initially free of Br.

Comparative oxidation feed (OF-e) describes a feed also containing 5.0wt % sugar with a relative distribution of 2:1 of fructose:glucose,providing a sugar composition of 3.3 wt % fructose and 1.7 wt % glucosein solution Water (20 wt % of total solution) was also added to theoxidation feed solution for OF-e to solubilize the sugars.

Step BB: Oxidation of Purified AcMF and HMF in Acetic Acid

A procedure similar to that described in step 1B was used except thatthe oxidation feeds of Step BA were used—with purified AcMF and HMF as asource of FDCA-forming furanics in an equivalent concentration to thefeeds used in Examples 1-4 (see Table 2, OF-c through OF-e).

Example B.1 demonstrates that inclusion of HBr in an oxidation feed(OF-d) with equivalent concentrations of HMF and AcMF to Example 1 doesnot alone replicate the high FDCA yields that are shown in Example 1.3using the integrated process with crude oxidation feed withoutpurification except filtration, even with comparable initial and finalBr loadings.

Comparative Examples B.2 and B.3 demonstrate initial catalyst conditionsequivalent to those present in Example 3.2. Again, substantiallydiminished FDCA yields are observed in Comparative Examples B.2 and B.3compared to Example 3.2. When comparing Comparative Example B.2 to B.3,it can also be shown that presence of sugar in the oxidation feed atconcentrations of 5 wt % does not lead to in situ dehydration andoxidation to form FDCA in substantial amounts.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1-23. (canceled) 24: An integrated process for producing one or moreesters of 2,5-furandicarboxylic acid from a six-carbon sugar-containingfeed, comprising: a) dehydrating a feed comprising a six-carbon sugarunit, in the presence of a bromine source and of a solvent, at anelevated temperature and for a time sufficient to generate an oxidationfeed comprised of at least one of 5-hydroxymethylfurfural and/or aderivative or derivatives of 5-hydroxymethylfurfural in the solvent,together with at least one bromine containing species; b) contacting theoxidation feed from step (a) with a homogeneous metal catalyst comprisedof one or more transition metals and bromine and with an oxygen sourceat an elevated temperature for a time sufficient to produce an oxidationproduct mixture comprising 2,5-furandicarboxylic acid (FDCA), thesolvent, and a residual catalyst; c) purifying and separating themixture obtained in step (b) to obtain FDCA and the solvent; d)recycling at least a portion of the solvent obtained in step (c) to step(a); e) recovering and reintroducing at least a portion of the one ormore transition metals and bromine for use in step b); and f)esterifying 2,5-furandicarboxylic acid from the oxidation productmixture with a C₁-C₁₂ aliphatic alcohol or a C₁-C₁₂ aliphatic diol,under conditions effective for carrying out the esterification andoptionally in the presence of a suitable esterification catalyst. 25:The process according to claim 24, further comprising regulating theamount of bromine in step (b) by adding to or removing brominecontaining species from the oxidation feed prior to step (b). 26: Theprocess according to claim 24, wherein the bromine containing species inthe oxidation feed comprise one or more of an inorganic bromide andorganic bromide. 27: The process according to claim 25, wherein thebromine containing species in the oxidation feed comprise one or more ofan inorganic bromide and organic bromide. 28: The process according toclaim 24, wherein the metal catalyst comprises either or both of Co andMn. 29: The process according to claim 28, wherein the metal catalystfurther comprises Zr. 30: The process according to claim 28, wherein themetal catalyst further comprises Ce. 31: The process according to claim24, wherein the bromine source comprises hydrogen bromide. 32: Theprocess according to claim 24, wherein the feed to the dehydration stepcomprises one or more of starch, amylose, galactose, cellulose,hemicellulose, inulin, fructan, glucose, fructose, sucrose, maltose,cellobiose, lactose, and sugar oligomers. 33: The process according toclaim 24, wherein the solvent comprises acetic acid or a mixture ofacetic acid and water. 34: The process according to claim 24, whereinthe feed is dehydrated in the further presence of a C₁-C₅ alcohol. 35:The process according to claim 24, further comprising regulating thewater content of the feed to the dehydration step and/or to theoxidation step. 36: The process according to claim 24, wherein theoxidation step is performed at a temperature of from about 120 to about250 degrees Celsius and at an oxygen partial pressure of from about 0.02to about 100 bar. 37: The process according to claim 24, wherein theesterification is conducted in the presence of an extrinsic acidic orbasic esterification catalyst. 38: The process according to claim 24,wherein the 2,5-furandicarboxylic acid is esterified by reacting the2,5-furandicarboxylic acid with a dialkylcarbonate in the presence of analcohol-containing solvent and without either an extrinsic acidic orbasic catalyst being present. 39: The process according to claim 24,wherein the 2,5-furandicarboxylic acid is esterified by reacting the2,5-furandicarboxylic acid with an alcohol in a liquid reaction systemin a CO₂-predominant atmosphere without the presence of any other acidcatalyst, under conditions corresponding to supercritical, critical, ornear-critical temperatures and pressures for the alcohol and/or forcarbon dioxide. 40: The process according to claim 24, furthercomprising preparing a polyester by transesterification of one or moreesters formed by the process of claim 1 with a C₂ to C₁₂ aliphatic diolor a polyol and optionally at least one of a polyalkylene ether glycol(PAEG), a polyfunctional acid, or a polyfunctional hydroxyl acid.